1. Field of the Invention
The present invention relates in general to improved polymeric packages having centrally disposed product containing portions, and more particularly relates to improved polymeric packaging of the type having a removable flange for opening a hermetically sealed, recloseable package.
2. The Prior Art
The prior art has included a wide variety of polymeric packages having recloseable features. Many of these packages are initially provided in a sealed condition, which have necessarily utilized a removable sealing mechanism to initially open the package.
Strippable mechanisms of prior art are set forth in, for example, U.S. Pat. No. 5,079,095, which discloses a peelable portion of a package lid, and which functions by delaminating polymeric webs.
U.S. Pat. No. 5,546,731 likewise depicts a polymeric package having an exteriorly disposed strippable or peelable package opening feature. This sealed package is also opened by delaminating one flange element from another.
Similar delaminating and/or strippable elements are set forth in the prior art, such as for example in U.S. Pat. No. 5,044,495 at FIG. 5.
Frequently in the prior art, polymeric packages of this kind have been hermetically sealed, such as for containing food or medical products which must be maintained in sterile condition. However, hermetically sealed packages with peelable seals have a tendency to open and/or leak readily during ambient barometric pressure drops or during air shipments, as well as transportation through high mountain passes. In that regard, peelable seals will open at 200-600 grams per lineal inch of full force. Higher peeling force materials have been attempted to cure this problem of premature seal fracture, but have often resulted in strip breakage during planned opening. It is believed that the mechanism of failure is such that when the ambient atmospheric pressure is reduced, the inner pressure of the package head space will burst the peelable seal open, causing comestible product contamination and spoilage, or contamination of sterile medical products.
In addition, the packages with an exteriorly disposed strippable or peelable package opening feature must be made from polymers that remain elastic at refrigerated temperatures of 32.degree. to 42.degree. F. (0.degree. to 5.5.degree. C.) without becoming brittle, or otherwise the removable strip will break. Polymers which will remain at refrigerated temperatures are more expensive and may have to contain plasticizers which are not desirable for packaging foods and medical devices.